A Look at Each Vaccine: MMR (Measles, Mumps and Rubella) Vaccine

MMR vaccine

Measles

The face of measles

Between 1990 and 1991 the city of Philadelphia was in the grip of a measles epidemic. At the center of the epidemic was a religious group that refused immunizations for themselves and their children. Children with measles developed high fever; a red, raised rash that started on the face and spread to the rest of the body; and "pink eye." For some, the disease got much worse. Seven children in the church developed a severe form of pneumonia as the measles virus infected their lungs. The lungs filled with pus — breathing became fast, labored and difficult. By the time these children were taken to the hospital, it was too late. They had died from measles.

What is measles?

Measles is a disease that is caused by a virus. Symptoms include fever, conjunctivitis ("pink eye"), and a red, pinpoint rash that starts on the face and spreads to the rest of the body. The rash lasts about five days. However, the virus can also cause pneumonia, a consequence that can lead to death. Although some people don't think of pneumonia as a common consequence of measles, it is actually quite common. Some older children infected with measles suffer from encephalitis (an infection of the brain), which, in many cases, causes permanent brain damage.

How is the measles vaccine made?

The measles vaccine is a live, "weakened" form of natural measles virus. To make some vaccines, viruses are "weakened" by a process called "cell culture adaptation" (see How Are Vaccines Made?). "Cell culture adaptation" modifies natural measles virus so that it behaves very differently once it is injected into the body.

Natural measles virus normally grows in cells that line the back of the throat, skin or lungs. Cells are the building blocks of all the different parts of the body, like skin, heart, muscles and lungs. Natural measles virus reproduces itself thousands of times, often causes severe disease, and is passed on to the next person unchanged.

But the process of "cell culture adaptation" changes all of that. Natural measles virus was first taken from someone infected with measles. The virus was then "grown" in cells taken from chick embryos. By growing the virus in chick embryo cells it became less and less able to grow in human cells. This happened because the genes that tell measles virus how to reproduce itself were changed. Now the virus reproduced itself very poorly.

When this vaccine virus (a now modified form of the natural virus) is put back into the body, it grows very poorly. Whereas natural measles virus reproduces itself thousands of times during natural infection, the measles vaccine virus reproduces itself probably fewer than 20 times. That is why natural measles virus causes illness, but measles vaccine virus doesn't. However, because the measles vaccine virus reproduces itself a little bit, it induces immunity against measles that is life-long. (see How Do Vaccines Work?).

The effectiveness of the measles vaccine has been dramatic. In 1962 (one year before the first measles vaccine was made available in the United States), 4 million people were diagnosed with measles, 48,000 were admitted to hospitals and 3,000 people died.

In 2012, 55 cases of measles were reported to the Centers for Disease Control and Prevention (CDC). While we were on the verge of eliminating measles from the United States, decreases in the use of the MMR vaccine have led to outbreaks; for example, outbreaks during 2011 led to about 220 cases of measles. Because most of the U.S. population is immune to measles, outbreaks can often, but not always, be traced to cases that result from international travel. Unfortunately, measles is one of the most contagious diseases; therefore, an infected person can quickly expose others who are susceptible.

What are the side effects of the measles vaccine?

Some children develop soreness in the local area of the shot, and occasionally a low-grade fever. Reports have also indicated rare cases of fevers greater than 103 degrees, usually five to 12 days after receiving the shot. Also some children develop a mild, measles-like rash about seven to 12 days after getting the measles vaccine. Children with this reaction can still get the measles vaccine in the future. Children with measles rash from the vaccine are not contagious to other people.

Because the measles vaccine is made in chick embryos, it was once thought that children with egg allergies should not receive the vaccine. This is no longer the case. Studies showed that even children with severe egg allergies could receive the measles vaccine without consequence.

Rarely, the combination measles-mumps-rubella (MMR) vaccine can also cause a short-lived decrease in the number of platelets that circulate in the body. Platelets are cells that help the blood to clot, such as, for example, after the skin is cut. This reaction occurs in roughly 1 of every 24,000 people who receive the vaccine and has never been fatal.

Why do children have to get two doses of MMR vaccine?

In the early 1990s, a second dose of the MMR vaccine was recommended. This recommendation was made because outbreaks of measles swept across the United States in the late 1980s and early 1990s. Most of the people who were infected with measles during these epidemics were adolescents and young adults. An investigation of what went wrong found that many people who caught measles had never been immunized. So the primary reason for recommending a second dose of MMR was to give children two chances to get one vaccine.

The other reason that a second dose of MMR vaccine was recommended was to allow for more children to develop a protective immune response. About 95 of every 100 children will develop immunity after one shot, but about 99 of 100 children will develop immunity to measles after two shots. Immunizing that additional 4 percent of children is important when trying to protect against a disease as highly contagious as measles.

The addition of mumps and rubella vaccines in this recommendation increases the percentage of children who develop immune responses to those viruses as well.

Should teenagers and adults get the MMR vaccine?

The MMR vaccine should be given to any teenager or adult who has not received two doses of the vaccine or has not had natural measles virus infection.

Do the benefits of the measles vaccine outweigh its risks?

Measles was almost eliminated from the United States. However, measles still rages throughout developing countries and is one of the leading causes of death worldwide. In the late 1980s and early 1990s in the United States, low immunization rates against measles were associated with epidemics of measles. About 11,000 people were hospitalized and 120 killed by measles virus. In recent years, we have started to again see outbreaks of measles. Because the measles vaccine has no serious permanent side effects, its benefits still clearly outweigh its risks.

Mumps

What is mumps?

Mumps is a virus that usually causes swelling in the salivary or parotid glands, just below the ear, lasting for about seven to 10 days. The chipmunk-like appearance of people infected with mumps is how mumps got its name.

But not all mumps infections were mild. Before the mumps vaccine, mumps was the most common cause of meningitis (inflammation of the lining of the brain and spinal cord). Virtually all children recovered from meningitis, but some were left with permanent deafness. Before the mumps vaccine, mumps was the most common cause of acquired deafness in the United States.

Mumps can also infect testicles and cause a disease known as orchitis. Some men with orchitis were found to be sterile after the infection resolved. Finally, mumps infection during pregnancy occasionally resulted in the death of the unborn child.

How is the mumps vaccine made?

Like the measles vaccine, the mumps vaccine is a live, "weakened" form of natural mumps virus. The mumps vaccine virus is "weakened" by a process called "cell culture adaptation." (see How Are Vaccines Made?). "Cell culture adaptation" modifies natural mumps virus so that it behaves very differently once it is injected into the body.

Natural mumps virus normally grows in cells of the salivary glands. Cells are the building blocks of all the different parts of the body, like skin, heart, muscles and lungs. Natural mumps virus reproduces itself thousands of times, occasionally causes severe disease, and is passed on to the next person unchanged.

But the process of "cell culture adaptation" changes all of that. Natural mumps virus was first taken from a little girl named Jeryl Lynn Hilleman. Jeryl Lynn was the daughter of Dr. Maurice Hilleman, a scientist who, at the time, was working in the research laboratories of a company named Merck, Sharpe & Dohme. Dr. Hilleman then "grew" the virus in eggs. By growing the virus in hen's eggs it became less and less able to grow in human cells. This happened because the genes that tell mumps virus how to reproduce itself were changed. Now the mumps virus reproduced itself very poorly.

When this vaccine virus (a now modified form of the natural virus) was put back into other children, it grew very poorly. Whereas natural mumps virus reproduces itself thousands of times during infection, the mumps vaccine virus reproduces itself probably fewer than 20 times. That is why natural mumps virus causes illness, but mumps vaccine virus doesn't. However, because the mumps vaccine virus reproduces itself a little bit, it induces immunity against mumps that is lifelong. (see How Do Vaccines Work?).

The strain of mumps virus used in the vaccine is called the "Jeryl Lynn" strain, in honor of Dr. Hilleman's daughter.

What are the side effects of the mumps vaccine?

Children may develop soreness in the local area of the shot, and occasionally a low-grade fever.

Because the mumps vaccine is made in eggs, it was once thought that children with egg allergies should not receive the vaccine. This is no longer the case. Studies showed that even those with severe egg allergies could receive the mumps vaccine without serious consequence.

Do the benefits of the mumps vaccine outweigh its risks?

In 2009 and 2010, a mumps outbreak that started at a summer camp affected more than 1,500 people. In 2012, the Centers for Disease Control and Prevention (CDC) had reports of about 200 cases of mumps. Because the mumps virus has the potential to infect the brain and cause permanent deafness, and the mumps vaccine does not have serious side effects, the benefits of the mumps vaccine outweigh its risks.

Rubella

The face of rubella

Before the rubella vaccine, children infected with rubella would develop a light, mild rash on the face. Some children would also develop swelling of the lymph glands behind the ear. Rubella was a mild infection of childhood. But in 1941, an Australian ophthalmologist made a curious observation. He found that many children were born with congenital cataracts and blindness following an outbreak of rubella. This was the evidence that rubella could permanently damage the developing fetus.

What is rubella?

Rubella is a viral infection also known as German measles. Rubella infection of children causes a mild rash on the face, swelling of glands behind the ear, occasionally a short-lived swelling of small joints (like the joints of the hand), and low-grade fever. Children virtually always recover from rubella infection without consequence.

But rubella is not always a mild infection. Before the rubella vaccine as many as 20,000 babies were born every year with birth defects because of the capacity of rubella virus to infect the unborn child. In fact, 85 of 100 women infected with rubella in the first trimester of pregnancy had babies that were permanently harmed. Rubella virus can cause blindness, deafness, heart defects or mental retardation in infants whose mothers were infected early in pregnancy.

How is the rubella vaccine made?

Like the measles and mumps vaccines, the rubella vaccine is a live, "weakened" form of natural rubella virus. The rubella vaccine virus is "weakened" by a process called "cell culture adaptation." (see How Are Vaccines Made?). "Cell culture adaptation" modifies natural rubella virus so that it behaves very differently once it is injected into the body.

Natural rubella virus normally grows in cells that line the back of the throat. Cells are the building blocks of all the different parts of the body, like skin, heart, muscles and lungs. Natural rubella virus reproduces itself thousands of times, occasionally causes severe disease, and is passed on to the next person unchanged.

But the process of "cell culture adaptation" changes all of that. Natural rubella virus was first taken from someone infected with rubella. The virus was then "grown" in human embryo fibroblast cells. These cells were first obtained from a therapeutic termination of one pregnancy in England in the early 1960s. These same embryonic cells have continued to grow in the laboratory and are used to make rubella vaccine today. Fibroblast cells are the cells needed to hold skin and other connective tissue together.

By growing rubella virus in human embryo fibroblast cells, it became less and less able to grow in human cells that lined the back of the throat or in cells of an unborn child. This happened because the genes that told rubella virus how to reproduce itself were changed. Now the virus reproduced itself very poorly.

When this vaccine virus (a now modified form of the natural virus) was put back into other children, it grew very poorly. Whereas natural rubella virus reproduced itself thousands of times during natural infection, the rubella vaccine virus reproduced itself probably fewer than 20 times. That is why natural rubella virus causes illness, but rubella vaccine virus doesn't. However, because the rubella vaccine virus reproduces itself a little bit, it induces immunity against rubella that is life-long. (see How Do Vaccines Work?).

There is probably no better example of how weakened the rubella vaccine virus is as compared with natural rubella virus than the following story: Rubella vaccine has been mistakenly given to pregnant women during their first trimester more than 1,000 times. No child born to these mothers was affected by the rubella vaccine. On the other hand, of 1,000 women infected with natural rubella infection during the first trimester, 850 will bear children with birth defects!

Girls are immunized with rubella vaccine to protect their future children

Rubella vaccine is a unique example of vaccinating one person to protect another. We vaccinate girls so that, if they become pregnant as adults, their unborn children will be protected against the devastating effects of rubella virus. We vaccinate boys to help stop the spread of rubella in the community.

What are the side effects of the rubella vaccine?

Some children experience soreness in the local area of the shot and a low-grade fever. Children may also develop a mild rash that is not contagious to other children.

The rubella vaccine can also cause arthritis (swelling and pain in the joints) in some women (usually those older than 14 years), but the arthritis is short-lived and doesn't cause permanent harm. The rubella vaccine is also an extremely rare cause of short-lived arthritis in young children.

Do the benefits of the rubella vaccine outweigh its risks?

In 2012, eight cases of rubella were reported to the CDC and three babies were born to women infected with rubella before coming to the U.S. One of the three babies died, and the remaining two will live with permanent disabilities. Rubella has been virtually eliminated from the United States; however, it is still quite common in many other regions (for example, China and Bangladesh). Because the rubella vaccine does not serious, permanent, side effects, the benefits of the rubella vaccine still outweigh its risks.

Materials in this section are updated as new information becomes available. The Vaccine Education Center staff regularly reviews materials for accuracy.

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